Frequency response improvement of a two-port surface acoustic wave device based on epitaxial AlN thin film

2017 2nd International Conference on Innovative Engineering Materials

Gao, Junning^1,2 ; Hao, Zhibiao^3 ; Luo, Yi^3 ; Li, Guoqiang^1,2

China State Key Laboratory of Luminescent Materials and Devices, School of Materials Science and Engineering, South China University of Technology, Guangzhou

510641, China^1

Engineering Research Center on Solid-State Lighting and Its Informationisation of Guangdong Province, South China University of Technology, Guangzhou

510641, China^2

Tsinghua National Laboratory for Information Science and Technology, Department of Electronic Engineering, Tsinghua University, Beijing

100084, China^3

关键词: Composite electrode;    Digital transducers;    Electromagnetic feedthrough;    Overall properties;    Pass-band ripples;    Piezoelectric substrates;    Propagation paths;    Surface acoustic wave (SAW);   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/284/1/012028/pdf
DOI  :  10.1088/1757-899X/284/1/012028

来源: IOP

【 摘 要 】

This paper presents an exploration on improving the frequency response of the symmetrical two-port AlN surface acoustic wave (SAW) device, using epitaxial AlN thin film on (0001) sapphire as the piezoelectric substrate. The devices were fabricated by lift-off processes with Ti/Al composite electrodes as interleaved digital transducers (IDT). The impact of DL and the number of the IDT finger pairs on the frequency response was carefully investigated. The overall properties of the device are found to be greatly improved with DL elongation, indicated by the reduced pass band ripple and increased stop band rejection ratio. The rejection increases by 8.3 dB when DL elongates from 15.5λ to 55.5λ and 4.4 dB further accompanying another 50λ elongation. This is because larger DL repels the stray acoustic energy out of the propagation path and provides a cleaner traveling channel for functional SAW, and at the same time restrains electromagnetic feedthrough. It is also found that proper addition of the IDT finger pairs is beneficial for the device response, indicated by the ripple reduction and the insertion loss drop.